Diswashing appliance and method of operation

ABSTRACT

A dishwashing appliance and method of operation are provided herein. The dishwashing appliance may include a heater operable to heat a tub of the dishwashing appliance. The method may include directing water into the tub, activating the heater by supplying electrical power to the heater, and adjusting the electrical power to the heater. Adjusting the electrical power may include detecting a temperature change within the tub, determining when the temperature change meets a predetermined criterion, and delivering a wattage output from the heater when the predetermined criterion is met.

FIELD OF THE INVENTION

The present subject matter relates generally to dishwashing appliances, and more particularly to heating assemblies for dishwashing appliances.

BACKGROUND OF THE INVENTION

Modern dishwashing appliances (e.g. dishwashers) typically include a tub defining a wash chamber where, for instance, detergent, water, and heat can be applied in order to clean food and/or other materials from dishes and other articles being washed. During wash and rinse cycles, dishwashers typically circulate a fluid through a wash chamber over articles such as pots, pans, silverware, and other cooking utensils. The fluid can be e.g., various combinations of water and detergent during the wash cycle or water (which may include additives) during the rinse cycle. Typically the fluid is recirculated during a given cycle using a pump. Fluid is collected at or near the bottom of the wash chamber and pumped back into the chamber through e.g., nozzles in the spray arms and other openings that direct the fluid against the articles to be cleaned or rinsed. Fluids used in e.g., the wash or rinse cycles may be heated. For example, hot water may be supplied to the dishwasher and/or the dishwasher may include one or more heat sources for heating fluids used in wash or rinse cycle and for providing heat during a drying cycle.

It is common to provide dishwashers with rod-type, resistive heating elements in order to supply heat within the wash chamber during one or more of the dishwasher cycles (e.g. during the drying cycle). Generally, these heating elements include an electric resistance-type wire that is encased in a magnesium oxide-filled, metallic sheath.

Typical dishwashers are configured to include a single wattage heater. For example, some dishwashers include a thousand (1000) watt heating element. Other dishwashers include an eight hundred (800) watt heating element. Higher watt heating elements may improve heating speeds. However, contents within the dishwashing appliance (e.g. dishes, glasses, utensils, etc.) may be damaged by prolonged exposure to high wattage heating. Also, managing temperature throughout the wash chamber can be difficult. Lower watt heating elements may decrease the risk of damage, but will generally increase the amount of time needed to heat water or articles within the wash chamber. Moreover, if any heat leaks from the wash chamber exist (e.g., due to insufficient sealing or insulation), lower watt heating elements will generally increase the overall amount of heat lost.

Thus, there is a need for a dishwashing appliance that can provide a consistent, safe performance across a range of temperatures.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In one aspect of the present disclosure a method of controlling a dishwashing appliance that includes heater operable to heat a tub of the dishwashing appliance is provided. The method may include directing water into the tub, activating the heater by supplying electrical power to the heater, and adjusting the electrical power to the heater. Adjusting the electrical power may include detecting a temperature change within the tub, determining when the temperature change meets a predetermined criterion, and delivering a wattage output from the heater when the predetermined criterion is met.

In another aspect of the present disclosure, a dishwashing appliance is provided. The dishwashing appliance may include a tub, a rack assembly, a resistive heating element, and a controller. The tub may define a wash chamber. The rack assembly may be disposed within the wash chamber of the tub. The rack assembly may be configured for supporting articles for washing within the wash chamber of the tub. The resistive heating element may be in thermal communication with the tub. The resistive heating element may be operable to heat the wash chamber. The controller may be operably connected to the resistive heating element. The controller may be configured to initiate adjusting the electrical power to the resistive heater. Adjusting the electrical power may include detecting a temperature change within the tub, determining when the temperature change meets a predetermined criterion, and delivering a wattage output from the heater when the predetermined criterion is met.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides a front view of a dishwashing appliance according to exemplary embodiments of the present disclosure.

FIG. 2 provides a cross-sectional side view of the exemplary dishwashing appliance of FIG. 1.

FIG. 3 provides a front perspective view of a sump portion of the exemplary dishwashing appliance of FIG. 1.

FIG. 4 provides a schematic view of a heating assembly of an example dishwashing appliance according to exemplary embodiments of the present disclosure.

FIG. 5 provides a flow chart illustrating a method of controlling a dishwashing appliance according to exemplary embodiments of the present disclosure.

FIG. 6 provides a flow chart illustrating a method of controlling a dishwashing appliance according to exemplary embodiments of the present disclosure.

FIG. 7 provides a flow chart illustrating a method of controlling a dishwashing appliance according to exemplary embodiments of the present disclosure.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Generally, the present disclosure may provide a dishwasher appliance and method of operation that can efficiently control the output of heat therein. The dishwasher appliance may include a heat source or heater that is configured to output a select amount of power within a wash chamber of the appliance. Specifically, the heat source may be a variable wattage heater. The appliance may be configured to vary the output wattage according to one or more conditions. For instance, the appliance may vary the output wattage so that a generally constant rate of temperature change in maintained.

Turning now to the figures, FIGS. 1 through 3 depict an exemplary domestic dishwasher appliance 100 that may be configured in accordance with aspects of the present disclosure. For the particular embodiment of FIGS. 1 through 3, the dishwasher appliance 100 includes a cabinet 102 having a tub 104 therein that defines a wash chamber 106. The tub 104 includes a front opening (not shown) and a door 120 hinged at its bottom 122 for movement between a normally closed vertical position (shown in FIGS. 1 and 2), wherein the wash chamber 106 is sealed shut for washing operations, and a horizontal open position for loading and unloading of articles from the dishwasher. Latch 123 is used to lock and unlock door 120 for access to wash chamber 106.

Upper and lower guide rails 124, 126 are mounted on tub side walls 128 and accommodate roller-equipped rack assemblies 130 and 132. In optional embodiments, each of the rack assemblies 130, 132 is fabricated into lattice structures including a plurality of elongated members 134 (for clarity of illustration, not all elongated members forming assemblies 130 and 132 are shown in FIG. 2). Each rack 130, 132 is adapted for movement between an extended loading position (not shown), in which the rack is substantially positioned outside the wash chamber 106, and a retracted position (shown in FIGS. 1 and 2), in which the rack is located inside the wash chamber 106. This rack movement is facilitated by rollers 135 and 139, for example, mounted onto racks 130 and 132, respectively. A silverware basket (not shown) may be removably attached to rack assembly 132 for placement of silverware, utensils, and the like that are otherwise too small to be accommodated by the racks 130, 132.

The dishwasher appliance 100 further includes a lower spray-arm assembly 144 that is rotatably mounted within a lower region 146 of the wash chamber 106 and above a tub sump portion 142 so as to rotate in relatively close proximity to rack assembly 132. In exemplary embodiments, such as the embodiment of FIGS. 1 and 2, one or more elevated spray assemblies 148, 150 are provided above the lower spray-arm assembly 144. For instance, a mid-level spray-arm assembly 148 is located in an upper region of the wash chamber 106 and may be located in close proximity to upper rack 130. Additionally or alternatively, an upper spray assembly 150 may be located above the upper rack 130.

The lower and mid-level spray-arm assemblies 144, 148 and the upper spray assembly 150 are part of a fluid circulation assembly 152 for circulating a wash fluid, such as water and/or dishwasher fluid, in the tub 104. In turn, fluid circulation assembly 152 may provide a flow of wash fluid within the wash chamber 106. For instance, fluid circulation assembly 154 includes a water inlet hose 172 in fluid communication with the wash chamber 106 (e.g., through a bottom wall and/or sidewall of tub 104) to supply water thereto. The sump portion 142 may thus be filled with water through a fill port 175 that outlets into wash chamber 106. A water supply valve 174 may be provided to control water to the wash chamber 106. Water supply valve 174 may have a hot water inlet 176 that receives hot water from an external source, such as a hot water heater and a cold water input 178 that receives cold water from an external source. It should be understood that the term “water supply” is used herein to encompass any manner or combination of valves, lines or tubing, housing, and the like, and may simply comprise a conventional hot or cold water connection.

The fluid circulation assembly 152 also includes a recirculation pump 154 positioned in a machinery compartment 140 located below the tub sump portion 142 (i.e., below a bottom wall) of the tub 104. The recirculation pump 154 receives fluid from sump 142 to provide a flow to assembly 152, or optionally, a switching valve or diverter (not shown) may be used to select flow. A heater 170 can be used to provide heat during, e.g., a wash, rinse, and/or drying cycle. Specifically, a variable wattage heater 170 may be included within dishwasher appliance 100. As will be described below, the heat or wattage output by heater 170 may be selectively varied during operation of the dishwashing appliance 100. Optionally, heater 170 may be a resistive heating element, such as a type sold under the name CALROD®. Additionally or alternatively, an inline heating element may be provided within fluid circulation assembly 152 to provide heat to wash fluid flowing therethrough.

Each spray-arm assembly 144, 148 includes an arrangement of discharge ports or orifices for directing washing fluid received from the recirculation pump 154 onto dishes or other articles located in rack assemblies 130 and 132. The arrangement of the discharge ports in spray-arm assemblies 144, 148 provides a rotational force by virtue of washing fluid flowing through the discharge ports. The resultant rotation of the spray-arm assemblies 144, 148 and the operation of the spray assembly 150 using fluid from the recirculation pump 154 provides coverage of dishes and other dishwasher contents with a washing spray. Other configurations of spray assemblies may be used as well.

In some embodiments, the dishwasher appliance 100 is further equipped with a controller 137 to regulate operation of the dishwasher appliance 100. The controller 137 may include one or more memory devices and one or more microprocessors, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with a cleaning cycle. The memory may represent random access memory such as DRAM or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. For certain embodiments, the instructions include a software package configured to operate appliance 100 and, e.g., execute the exemplary methods 500, 600, and/or 700 described below with reference to FIGS. 5 through 7. The memory may be a separate component from the processor or may be included onboard within the processor. Alternatively, controller 137 may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software.

One or more temperature sensors 180 (e.g., thermistor or thermocouple) may be provided in operable communication with (e.g., electrically coupled to) controller 137. Optional temperature sensors 180 may be mounted within tub 104. In the illustrated exemplary embodiments of FIG. 2, temperature sensors 180 are mounted within wash chamber 106 and sump portion 142 to detect the temperature of the air and/or wash fluid within tub 104.

The controller 137 may be positioned in a variety of locations throughout dishwasher appliance 100. In the illustrated embodiment, the controller 137 may be located within a control panel area 121 of door 120 as shown in FIGS. 1 and 2. In some such embodiments, input/output (“I/O”) signals may be routed between the control system and various operational components of dishwasher appliance 100 along one or more wiring harnesses that may be routed through the bottom 122 of door 120. Optionally, the controller 137 includes a user interface panel/controls 136 through which a user may select various operational features and modes and monitor progress of the dishwasher appliance 100. In exemplary embodiments, the user interface 136 may represent a general purpose I/O (“GPIO”) device or functional block. For instance, the user interface 136 may include input components, such as one or more of a variety of electrical, mechanical, or electro-mechanical input devices including rotary dials, push buttons, and touch pads. The user interface 136 may include a display component, such as a digital or analog display device designed to provide operational feedback to a user. The user interface 136 may be in communication with the controller 137 via one or more signal lines or shared communication busses.

In some embodiments, controller 137 is in communication with heater 170 and/or sensors 180 via one or more signal lines or shared communication busses. Moreover, controller 137 is generally configured to selectively the wattage of heater 170. For instance, controller 137 may be configured to initiate adjustments of electrical power to heater 170. As will be described in detail below, adjustments of electrical power may be based on a detected temperature change, e.g., from temperature sensors 180, and/or one or more predetermined criteria.

It should be appreciated that the invention is not limited to any particular style, model, or configuration of dishwasher. The exemplary embodiment depicted in FIGS. 1 through 3 is for illustrative purposes only. For example, different locations may be provided for user interface 136, different configurations may be provided for racks 130, 132, and other differences may be applied as well.

Turning to FIG. 4, an exemplary heating assembly 200, including a control circuit 202 is provided. As illustrated, controller 137 may be operably connected to control circuit 202 to selectively vary or adjust the electrical power delivered to a heating element 201. As will be understood, heating element 201 may include the resistive heater 170 described above with respect to FIGS. 1 and 2. During operation, controller 137 may effectively control a wattage output of heating element 201. In optional embodiments, heating element 201 is provided within a heat circuit 204. A voltage source 208 and switching element 206 may be additionally disposed within the heat circuit 204, such that each element 201, 206, and 208 is electrically coupled, e.g., in series. Switching element 206 may be a solid state thyristor, such as a TRIAC. Controller 137 may be operably connected to switching element 206. Power or wattage to heating element 201 may be varied, for instance, by selectively activating switching element 206 to cycle an A/C voltage from voltage source 208. Voltage to heating element 201 may thus be rapidly cycled off and on according to the state of the switching element 206. Continuous (i.e., non-cycled) operation of heating element 201 will generally correspond to a higher wattage output of heating element 20 (in comparison to cycled operation, in which power to heating element 201 is restricted). As power or wattage to heating element 201 is varied, the wattage output of heating element 201 may thus be adjusted.

Turning now to FIGS. 5 through 7, various methods 500, 600, and 700 for operating a dishwashing appliance are illustrated. Methods 500, 600, and 700 may be used to operate any suitable dishwashing appliance. As an example, some or all of methods 500, 600, and 700 may be used to operate dishwashing appliance 100 (FIG. 1). The controller 137 (FIG. 2) may be programmed to implement some or all of methods 500, 600, and 700.

Turning specifically to FIG. 5, an optional method 500 of controlling a dishwashing appliance is provided. At 510, the method 500 includes directing water into the tub of the dishwashing appliance. For instance, water may be flowed into a wash chamber of the tub to aid in cleaning items (e.g., utensils) within the tub. Specifically, water may be flowed from a fluid circulation assembly and/or a fluid inlet hose, as described above.

At 520, the method 500 includes activating the heater by supplying electrical power to the heater. The heater of some embodiments includes a resistive heat element, as described above, that receives the supplied electrical power. The supplied power may thus generate heat when received by the heater.

Once the heater is activated, the method 500 may provide for adjusting electrical power to the heater, e.g., according to one or more conditions. At 530, the method 500 includes detecting a temperature change within the tub. One or more temperature sensors disposed within the tub may monitor the temperature therein. For instance, 530 may include monitoring a temperature of water flowing through a sump portion of the dishwashing appliance, e.g., from a temperature sensor mounted within the sump portion. Additional or alternatively, 530 may include monitoring a temperature of air within the wash chamber of the dishwashing appliance, e.g., from a temperature sensor mounted within the wash chamber. Temperature measurements may be received by the controller intermittently or continuously. In some embodiments, the controller collects temperature measurements, e.g., as temperature signals from a temperature sensor, according to a preset pattern. For instance, a predetermined time period between temperature measurements may be set. The difference between two temperature measurements, e.g., two successive temperature measurements, may be calculated over the predetermined time period. In optional embodiments, the change in temperature is a calculated increase rate. In other words, the rate of temperature increase over the predetermined period of time.

At 540, the method 500 includes determining when the temperature change meets one or more predetermined criteria. For instance, the measured rate of temperature change may be evaluated for agreement with a predetermined criterion. In some embodiments, the predetermined criterion is a conditional requirement for subsequent adjustments to the electrical power being delivered to the heater. The predetermined criterion may be a target temperature change, e.g., a target value for the rate of temperature increase. Optionally, 540 may include determining whether the detected temperature change of 530 meets the target temperature change.

At 550, the method 500 includes delivering a wattage output from the heater. Specifically, the wattage output may be delivered to and subsequently from the heater only when the predetermined condition is met. In some embodiments, the wattage output is a set incremental adjustment in power or wattage output being delivered from the heater. Set incremental adjustments may be made according to the determination of 540. Wattage output may be increased, e.g., from an initial or current wattage output value, when it is determined that the detected temperature change is less than the target temperature change. Wattage output may be decreased e.g., from the initial or current wattage output value, when it is determined that the detected temperature change is greater than the target temperature change. In specific embodiments, increasing power includes increasing power by a preset wattage value. In other words a preset wattage increment. In additional or alternative embodiments, decreasing power includes decreasing power by a preset wattage value. The amount of preset wattage value of increasing power may be identical or distinct from the amount of preset wattage value of decreasing power.

In some embodiments, method 500 includes actively adjusting the electrical power to the heater according to a predetermined pattern. Specifically, the method 500 may provide for repeatedly adjusting the electrical power to (and output from) the heater. After a single or first adjustment to electrical power is made, e.g., at 550, steps 530 through 550 may be repeated. A pattern or sequence for each repetition may be provided. For instance, a set amount of time may be provided for repeating steps 530 through 550. After 550 is completed, 530 may not be repeated until the set amount of time elapses. In optional embodiments, the target temperature change remains constant for each repeated adjustment. A continuous loop may thus be established to maintain a constant target temperature change (e.g., rate of temperature increase) throughout the operation (or a cycle thereof) for the dishwashing appliance.

In certain embodiments, the method 500 includes initiating a wash cycle of the dishwashing appliance. Adjusting the electrical power to the heater, e.g., 530 through 550, may occur during the wash cycle. In additional or alternative embodiments, the method 500 includes initiating a dry cycle of the dishwashing appliance. Adjusting the electrical power to the heater, e.g., 530 through 550, may occur during the dry cycle. In further additional or alternative embodiments, adjusting the electrical power to the heater, e.g., 530 through 550, occurs during the wash cycle. The delivered wattage output may be a relatively high wattage output. The dry cycle may take place after the wash cycle and include initiated a relatively low wattage output from the heater (i.e., a wattage output that is less than the relatively high wattage output).

Turning now to FIG. 6, an optional method 600 of controlling a dishwashing appliance is provided. At 610, the method 600 includes initiating a cleaning sequence. At 610, a wash or rinse cycle may subsequently begin by directing water into the tub of the dishwashing appliance. As shown, at 610 the method 600 includes activing a wash pump and heater of the dishwashing appliance once water has been directed into the tub. Activating the heater may include providing an initial output wattage from the heater.

At 620, the method 600 includes monitoring temperature over a predetermined period, e.g., a predetermined period of time. For instance, the temperature of water through a sump portion of the dishwashing appliance may be monitored over the predetermined period. Monitoring at 620 may include detecting a rise in temperature between a first temperature measurement and second temperature measurement. The first temperature measurement may be obtained at the start of the predetermined period while the second temperature measurement is obtained at the end of the predetermined period.

At 630, the method 600 includes actively adjusting the output wattage of the heater. Specifically, a rate of temperature increase may be calculated, e.g., from the change in temperature over the predetermined period. Immediately after 620, the difference between the first temperature measurement and the second temperature measurement may provide a rate of temperature increase. Once a calculated rate of temperature increase is obtained, the calculated rate may be compared to a predetermined criterion. In some such embodiments, the predetermined criterion includes a requirement that the calculated rate equal to (or approximately equal to) a target rate. As used herein within the context of a rate, the term “approximately” means within five percent (5%).

If is determined that the calculated rate does not equal the target rate, 630 may include determining if the calculated rate is less than the target rate. If the calculated rate is less than target rate, wattage output by the heater is increased by a preset value, e.g., from the initial or current output wattage. If the calculated rate is not less than the target rate, wattage output by the heater is decreased by a preset value e.g., from the initial or current output wattage. The preset value for increasing power may be identical to the preset value for decreasing power. Once the output wattage is increased or decreased, a new rate of temperature increase may be calculated, e.g., over a predetermined period.

If it is determined that the calculated rate does equal the target rate, 630 may include determining if a wash cycle is complete. In some such embodiments, wash cycle completion is tied to expiration of a wash period. In other embodiments, wash cycle completion is tied to a condition within the wash chamber, e.g., turbidity of water therein. If the wash cycle is not complete, a new rate of temperature increase is calculated, e.g., over a predetermined period. If the wash cycle is complete, the method 600 may provide for advancing to step 640.

At 640, the method 600 includes initiating a dry cycle. Specifically, 640 includes deactivating the wash pump and the heater. Additionally water is drained from the tub. In other words, most of the collected water or wash fluid within the wash chamber, e.g., at the sump portion, is removed to a drain or the ambient environment. Subsequently, the heater may be again activated to promote evaporation of residual moisture within wash chamber. Optionally, the heater may be activated at an output wattage that is lower than the output wattage of 630, e.g., lower than the initial output wattage and/or than the wattage output at the end of 630. In turn, the output wattage of 640 may be a relatively low output wattage, while the wattage output of 630 is a relatively high wattage output. Upon reaching a predetermined dry state, the heater may be deactivated and the cleaning sequence may be ended.

Turning now to FIG. 7, an optional method 700 of controlling a dishwashing appliance is provided. At 710, the method 700 includes initiating a cleaning sequence. At 710, a wash or rinse cycle may subsequently begin by directing water into the tub of the dishwashing appliance. As shown, at 710 the method 700 includes activing a wash pump and heater of the dishwashing appliance once water has been directed into the tub. The wash pump and heater may operate continuously or intermittently to complete a predetermined cycle, e.g., wash or rinse cycle.

At 720, the method 700 includes initiating a dry cycle. Specifically, 720 includes deactivating the wash pump and heater. Additionally water is drained from the tub. In other words, most of the collected water or wash fluid within the wash chamber, e.g., at the sump portion, is removed to a drain or the ambient environment. Subsequently, the heater may be again activated to transfer heat to the air and promote evaporation of residual moisture within wash chamber. Activating the heater may include providing an initial output wattage from the heater.

At 730, the method 700 includes monitoring temperature over a predetermined period. For instance, the temperature of air within the wash chamber of the dishwashing appliance may be monitored over the predetermined period of time. Monitoring at 730 may include detecting a rise in temperature between a first temperature measurement and second temperature measurement. The first temperature measurement may be obtained at the start of the predetermined period while the second temperature measurement is obtained at the end of the predetermined period.

At 740, the method 700 includes actively adjusting the output wattage of the heater. Specifically, a rate of temperature increase may be calculated, e.g., from the change in temperature over the predetermined period of time. Immediately after 730, the difference between the first temperature measurement and the second temperature measurement over the predetermined period may provide a rate of temperature increase. Once a calculated rate of temperature increase is obtained, the calculated rate may be compared to a predetermined criterion that includes a requirement that the calculated rate equal to (or approximately equal to) a target rate.

If is determined that the calculated rate does not equal the target rate, 740 may include determining if the calculated rate is less than the target rate. If the calculated rate is less than target rate, wattage output by the heater is increased by a preset value, e.g., from the initial or current output wattage. If the calculated rate is not less than the target rate, wattage output by the heater is decreased by a preset value e.g., from the initial or current output wattage. The preset value for increasing power may be identical to the preset value for decreasing power. Once the output wattage is increased or decreased, a new rate of temperature increase may be calculated, e.g., over a predetermined period.

If it is determined that the calculated rate does equal the target rate, 740 may include determining if a dry cycle is complete. In some such embodiments, dry cycle completion is tied to expiration of a dry period. In other embodiments, dry cycle completion is tied to a condition within the wash chamber, e.g., temperature within the wash chamber. If the dry cycle is not complete, a new rate of temperature increase is calculated, e.g., over a predetermined period. If the dry cycle is complete, the cleaning sequence may be ended.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A method of controlling a dishwashing appliance, the dishwashing appliance comprising a heater operable to heat a tub of the dishwashing appliance, the method comprising: directing water into the tub; activating the heater by supplying electrical power to the heater; and adjusting the electrical power to the heater, comprising: detecting a temperature change within the tub, determining when the temperature change meets a predetermined criterion, and delivering a wattage output from the heater when the predetermined criterion is met.
 2. The method of claim 1, wherein detecting the temperature change within the tub comprises measuring a rate of temperature increase over a predetermined period of time.
 3. The method of claim 2, wherein measuring the rate of temperature increase over the predetermined period of time comprises monitoring a temperature of water flowing through a sump portion of the dishwashing appliance.
 4. The method of claim 1, further comprising initiating a wash cycle of the dishwashing appliance, wherein adjusting the electrical power to the heater occurs during the wash cycle.
 5. The method of claim 1, further comprising initiating a dry cycle of the dishwashing appliance, wherein adjusting the electrical power to the heater occurs during the dry cycle.
 6. The method of claim 1, wherein the predetermined criterion is a target temperature change, and wherein determining when the temperature change meets the predetermined criterion comprises determining that the detected temperature change meets the target temperature change.
 7. The method of claim 6, wherein delivering the wattage output from the heater comprises: increasing the wattage output when the detected temperature change is less than the target temperature change; and decreasing the wattage output when the detected temperature change is greater than the target temperature change.
 8. The method of claim 7, wherein increasing the wattage output comprises increasing power to the heater according to a preset wattage value, and wherein decreasing the wattage output comprises decreasing power to the heater according to a preset wattage value.
 9. The method of claim 6, further comprising repeatedly adjusting the electrical power to the heater according to a predetermined pattern.
 10. The method of claim 1, further comprising initiating a wash cycle of the dishwashing appliance; and initiating a dry cycle of the dishwashing appliance; wherein adjusting the electrical power to the heater occurs during the wash cycle, wherein the delivered wattage output is a high wattage output, and wherein the dry cycle includes initiating a low wattage output from the heater.
 11. A dishwashing appliance comprising: a tub defining a wash chamber; a rack assembly disposed within the wash chamber of the tub, the rack assembly configured for supporting articles for washing within the wash chamber of the tub; a resistive heating element in thermal communication with the tub, the resistive heating element being operable to heat the wash chamber; and a controller operably connected to the resistive heating element, the controller being configured to initiate adjusting the electrical power to the resistive heater, adjusting the electrical power comprising: detecting a temperature change within the tub, determining when the temperature change meets a predetermined criterion, and delivering a wattage output from the heater when the predetermined criterion is met.
 12. The dishwashing appliance of claim 11, wherein detecting the temperature change within the tub comprises measuring a rate of temperature increase over a predetermined period of time.
 13. The dishwashing appliance of claim 12, wherein measuring the rate of temperature increase over the predetermined period of time comprises monitoring a temperature of water flowing through a sump portion of the dishwashing appliance.
 14. The dishwashing appliance of claim 11, wherein the controller is further configured to initiate a wash cycle, and wherein adjusting the electrical power to the heater occurs during the wash cycle.
 15. The dishwashing appliance of claim 11, wherein the controller is further configured to initiate a wash cycle, wherein adjusting the electrical power to the heater occurs during the dry cycle.
 16. The dishwashing appliance of claim 11, wherein the predetermined criterion is a target temperature change, and wherein determining when the temperature change meets the predetermined criterion comprises determining that the detected temperature change meets the target temperature change.
 17. The dishwashing appliance of claim 16, wherein delivering the wattage output from the heater comprises: increasing the wattage output when the detected temperature change is less than the target temperature change, and decreasing the wattage output when the detected temperature change is greater than the target temperature change.
 18. The dishwashing appliance of claim 17, wherein increasing the wattage output comprises increasing power to the heater according to a preset wattage value, and wherein decreasing the wattage output comprises decreasing power to the heater according to a preset wattage value.
 19. The dishwashing appliance of claim 11, wherein the controller is further configured to initiate repeatedly adjusting the electrical power to the heater according to a predetermined pattern.
 20. The dishwashing appliance of claim 11, wherein the controller is further configured to: initiate a wash cycle of the dishwashing appliance, and initiate a dry cycle of the dishwashing appliance, wherein adjusting the electrical power to the heater occurs during the wash cycle, wherein the delivered wattage output is a high wattage output, and wherein the dry cycle includes initiating a low wattage output from the heater. 